Field of the Invention
The present invention relates to a method of manufacturing hexagonal ferrite powder, hexagonal ferrite powder, and a magnetic recording medium
Discussion of the Background
Hexagonal ferrite powder is widely employed as ferromagnetic powder contained in a magnetic layer of magnetic recording media. The coercive force thereof is great enough for use in permanent magnetic materials. The magnetic anisotropy that is the basis of the coercive force derives from its crystal structure. Thus, high coercive force can be maintained even when the size of the particles is reduced. Further, magnetic recording media employing hexagonal ferrite in a magnetic layer have high density characteristics due to the vertical component. Thus, hexagonal ferrite is ferromagnetic powder that is suited to high density recording.
Various methods of manufacturing hexagonal ferrite have been proposed, including the coprecipitation method, the hydrothermal synthesis method, and the glass crystallization method. Of these, manufacturing methods utilizing a hydrothermal synthesis reaction (referred to as a hydrothermal synthesis process, hereinafter) in the presence of a high-temperature, high-pressure water such as supercritical water and subcritical water have been garnering attention in recent years as methods permitting the manufacturing of hexagonal ferrite with high productivity (for example, see Japanese Unexamined Patent Publication (KOKAI) No. 2009-208969, which is expressly incorporated herein by reference in its entirety).